In providing filler cap assemblies for vehicle fuel tanks, for example trucks, it is desirable that the cap be manually operable without tools for refueling. The cap must be removed when refueling is necessary and securely refastened and sealed into the tank opening after refueling.
A typical prior art filler cap assembly is disclosed in U.S. Pat. No. 3,391,817. Assemblies of this type include a filler cap having a cover adapted to telescopically seat within a fuel tank opening defined by annular shaped walls. A seal between the cap and the tank opening is effected along the inner peripheral surface of the annular shaped walls.
The filler cap assembly as disclosed in the above-referenced patent comprises a cover with a lower face adapted to be received within the opening of the tank. A retaining member connected to the lower face of the cover cooperates with the walls of the tank opening to fasten the cap within the opening. The lower face is further constructed to prevent rotation of the cover relative to the tank opening.
The upper end of the cover is adapted to face in an outwardly direction. An operating handle is disposed at the upper face of the cover and is connected to the retaining member by an axle. Operation of the handle moves the retaining member between its fastened and unfastened positions with respect to the opening. Seal means are attached to the cover of the cap for sealing engagement with the surrounding tank walls of the opening when the retaining member is in the fastened position.
High fuel costs are encouraging fuel theft. It is often desirable to provide lock means to lock the fastened fuel cap assemblies to fuel tanks. Prior art lock means for the above disclosed caps comprise lock cylinders which lock the operating handle to the cover. Unfortunately such lock means can be circumvented by breaking off the handle with the impact force of a hammer and turning the axle with a pair of pliers to rotate the retaining member to its unfastened position.